1. Field of the Invention
The present invention relates to an articulated industrial robot.
2. Description of the Related Art
There exists a need to reduce the size of an articulated industrial robot. On the other hand, a need exists to provide space for replacing a robot component, for example, a motor. In view of these needs, it is important that not only the size of the robot but also the installation space for the robot, including the space allowed for replacement work, be reduced.
An industrial robot is known which is constructed so that a motor can be removed for replacement by moving the motor slidingly along the direction of its axis (for example, refer to Japanese Unexamined Patent Publication No. 2013-006271).
FIG. 14 shows a joint unit 116 of a robot according to the prior art. The joint unit 116 includes a motor 120, a speed reduction mechanism 140, and a supporting member 130 for supporting the motor 120 and the speed reduction mechanism 140. A motor shaft 124 is provided at the end with a gear 142. The gear 142 engages with the speed reduction mechanism 140 which is connected to a driven member driven by the motor 120 so that power is transmitted from the motor 120 to the driven member.
When removing the motor 120 from the supporting member 130 for such purposes as replacement or inspection of the motor 120, the motor 120 is first moved in the direction of its axis (see arrow A in FIG. 14) to detach it from the supporting member 130, and the motor 120 is then moved slidingly along a direction (see arrow B in FIG. 14) at a right angle to the axial direction.
Therefore, the motor 120 cannot be removed from the supporting member 130 smoothly, unless the overall length L1′ of the motor 120 is smaller than the dimension L2′ of the interior space of the supporting member 130 measured along the axis direction. FIG. 15 shows the case in which the relation L1′<L2′ is true; in this case, the motor 120 can be easily removed from the supporting member 130.
On the other hand, FIG. 16 shows the case in which the relation L1′>L2′ is true; in this case, the motor 120 cannot be removed from the supporting member 130, because the motor shaft 124 or the gear 142 interferes with the supporting member 130.
FIG. 17 shows a portion of the configuration of a robot 100 according to the prior art. The robot 100 includes a first supporting member 230 and a second supporting member 330. The first supporting member 230 supports a first motor 220 and a first speed reduction mechanism 240. The second supporting member 330 supports a second motor 320 and a second speed reduction mechanism 340.
As in the above-described prior art, the first motor 220 can be removed from the first supporting member 230 by pulling it in the direction of its axis (see arrow A in FIG. 17). However, in the configuration shown here, since the second motor 320 is located in the axial direction of the first motor 220, the first motor 220 may interfere with the second motor 320 when removing the first motor 220 from the first supporting member 230.
Referring to FIG. 18, there is shown the case in which the distance L2′ from the mounting surface of the first motor 220 to the second motor 320 is shorter than the overall length L1′ of the first motor 220. In this case, when trying to remove the first motor 220 from the first supporting member 230, the first motor 220 interferes with the second motor 320. Accordingly, when replacing the first motor 220, the second motor 320 must also be removed, which can degrade the work efficiency or can cause damage to the first motor 220 or the second motor 320.
In contrast, in the example shown in FIG. 19, the second supporting member 330 is enlarged to ensure a sufficient distance between the first supporting member 230 and the second motor 320. In this case, the first motor 220 can be removed from the first supporting member 230 without causing interference with the second motor 320. However, since the second supporting member 330 is enlarged, the size of the robot 100 correspondingly increases, resulting in an inability to address the need for size reduction.